#pragma once
#include <string.h>
#include <stdint.h>

namespace proto {
// header - addr - len - TLV0 - TLV1 - ... - TLVn - crc16

constexpr uint8_t FrameHeader = 0x55;
constexpr uint8_t FrameAddrDevice = 0x00;
constexpr uint8_t FrameAddrHost = 0x01;

enum class FrameTag : uint8_t {
	/////// host --> device ///////
    // [tag][00]
	ResetTimeBase = 0,
    // [tag][01][start(1)]
    // [tag][01][stop(0)]
	LedStatusReportCfg,
    // [tag][01][fdc(0~255)]
	PwmFixedDutyCycle,
    // [tag][02][period_low][period_high]
	PwmSawtoothWave,
	PwmTriangleWave,
	PwmSinWave,

    /////// device --> host /////// 
    // [tag][2][data_crc0][data_crc1]
    DataAck = 100,
    // [tag][03][light(0~255)][t0][t1]
    // [tag][04][light(0~255)][t0][t1][t2]
    // [tag][05][light(0~255)][t0][t1][t2][t3]
	ReportLedStatus
};

static uint8_t Tag2Num(FrameTag tag) {
    return static_cast<uint8_t>(tag);
}

/* 
* The crc32 is licensed under the Apache License, Version 2.0, and a copy of the license is included in this file.
*  CRC16 implementation according to CCITT standards.
*
* The XMODEM CRC 16 algorithm, using the following parameters:
*
* Name                       : "XMODEM", also known as "ZMODEM", "CRC-16/ACORN"
* Width                      : 16 bit
* Poly                       : 1021 (That is actually x^16 + x^12 + x^5 + 1)
* Initialization             : 0000
* Reflect Input byte         : False
* Reflect Output CRC         : False
* Xor constant to output CRC : 0000
* Output for "123456789"     : 31C3
*/

static constexpr uint16_t crc16tab[256]= {
    0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
    0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
    0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,
    0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,
    0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,
    0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,
    0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,
    0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,
    0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,
    0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,
    0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,
    0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,
    0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,
    0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,
    0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,
    0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,
    0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,
    0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,
    0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,
    0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,
    0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,
    0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,
    0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,
    0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,
    0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,
    0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,
    0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,
    0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,
    0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,
    0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,
    0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,
    0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0
};

static uint16_t crc16(const uint8_t *buf, size_t len) {
    uint16_t crc = 0;
    for (size_t counter = 0; counter < len; counter++)
        crc = (crc<<8) ^ crc16tab[((crc>>8) ^ *buf++)&0x00FF];
    return crc;
}

class FrameAssembler {
public:
    explicit FrameAssembler(uint8_t buffer[256], uint8_t addrVal)
        : targetAddr(addrVal)
        , frameBuffer(buffer)
        , frameLen(0)
    {
        ClearFrame();
    }

    uint8_t* GetFrame(size_t &len) {
        len = 0;
        if (frameLen == 0) {
            return nullptr;
        }
        len = frameLen;
        return frameBuffer;
    }

    void ClearFrame() {
        memset(frameBuffer, 0, 256);
        frameBuffer[0] = FrameHeader;
        frameBuffer[1] = targetAddr;
        frameBuffer[2] = 0;
        frameLen = 3;
    }

    bool AppendTLV(uint8_t tag, uint8_t len, const uint8_t* val) {
        if (len > 248 || frameLen > 252) {
            return false;
        }
        if (len > 0 && !val) {
            return false;
        }
        if (size_t(253) - frameLen < len + size_t(2)) {
            return false;
        }
        frameBuffer[frameLen] = tag;
        frameLen++;
        frameBuffer[frameLen] = len;
        frameLen++;
        if (len > 0) {
            memcpy(&frameBuffer[frameLen], val, len);
            frameLen += len;
        }
        return true;
    }

    bool AppendTagOnly(uint8_t tag) {
        return AppendTLV(tag, 0, nullptr);
    }

    bool AppendCRC() {
        if (frameLen < 4 || frameLen >= 254) {
            return false;
        }
        frameBuffer[2] = static_cast<uint8_t>(frameLen - 1);
        auto crc = crc16(frameBuffer, frameLen);
        frameBuffer[frameLen] = static_cast<uint8_t>(crc & 0xff);
        frameLen++;
        frameBuffer[frameLen] = static_cast<uint8_t>(crc >> 8);
        frameLen++;
        return true;
    }

private:
    const uint8_t targetAddr;
    uint8_t* frameBuffer;
    size_t frameLen;
};

class FrameDecoder {
public:
    using TlvReportCallback = bool (*)(void* userdata, uint8_t t, uint8_t l, const uint8_t *v);
    enum class Status {
        Drop = 0,
        Header,
        Addr,
        FrameLen,
        Tag,
        Len,
        Value,
        CrcLowByte,
        FrameEnd,
        BadCrc,
        DecodeFailed
    };

    explicit FrameDecoder(uint8_t buffer[256], uint8_t addrVal, bool skipCrcVer = false)
        : skipCrcVerify(skipCrcVer)
        , targetAddr(addrVal)
        , frameBuffer(buffer)
        , frameLen(0)
    {
        Reset();
    }

    void Reset() {
        memset(frameBuffer, 0, 256);
        frameLen = 0;
        frameDataLen = 0;
        curTlvLen = 0;
        innerState = InnerState::WaitHeader;
    }

    Status AppendByte(uint8_t val) {
        return Dispatch(val);
    }

    int GetTLVs(TlvReportCallback cbTlvReport = nullptr, void* userdata = nullptr) const {
        if (innerState != InnerState::WaitDataRetrive) {
            return 0;
        }
        int tlvCnt = 0;
        const auto *pcrc = frameBuffer + frameBuffer[2] + 1;
        const auto *ptr = frameBuffer + 3;
        while (ptr < pcrc) {
            tlvCnt++;
            auto t = ptr[0];
            auto l = ptr[1];
            if (cbTlvReport) {
                auto v = l > 0 ? (ptr + 2) : nullptr;
                if (!cbTlvReport(userdata, t, l, v)) {
                    break;
                }
            }
            ptr += l + 2;
        }
        return tlvCnt;
    }

private:
    enum class InnerState {
        WaitHeader = 0,
        WaitAddr,
        WaitFrameDataLen,
        WaitTag,
        WaitLen,
        WaitValue,
        WaitCrc16LowByte,
        WaitCrc16HighByte,
        WaitDataRetrive,
        StopOnDeath
    };

    Status Dispatch(uint8_t val) {
        switch (innerState)
        {
        case InnerState::WaitHeader:
            if (val != FrameHeader) {
                return Status::Drop;
            }
            AcceptByte(val);
            innerState = InnerState::WaitAddr;
            return Status::Header;

        case InnerState::WaitAddr:
            AcceptByte(val);
            innerState = InnerState::WaitFrameDataLen;
            return Status::Addr;

        case InnerState::WaitFrameDataLen:
            if (val > 252 || val < 4) {
                return DeadState();
            }
            AcceptByte(val);
            frameDataLen = val;
            innerState = InnerState::WaitTag;
            return Status::FrameLen;

        case InnerState::WaitTag:
            AcceptByte(val, true);
            if (frameDataLen < 3) {
                // len-crc0-crc1
                return DeadState();
            }
            innerState = InnerState::WaitLen;
            return Status::Tag;

        case InnerState::WaitLen:
            if (val > 248) {
                return DeadState();
            }
            AcceptByte(val, true);
            if (frameDataLen < val + 2) {
                // [val]-crc0-crc1
                return DeadState();
            }
            curTlvLen = val;
            if (val > 0) {
                innerState = InnerState::WaitValue;
            }
            else if (frameDataLen > 2) {
                // next tlv
                innerState = InnerState::WaitTag;
            }
            else {
                innerState = InnerState::WaitCrc16LowByte;
            }
            return Status::Len;

        case InnerState::WaitValue:
            AcceptByte(val, true, true);
            if (curTlvLen > 0) {
                return Status::Value;
            }
            else if (frameDataLen > 2) {
                // next tlv
                innerState = InnerState::WaitTag;
            }
            else {
                innerState = InnerState::WaitCrc16LowByte;
            }
            return Status::Value;

        case InnerState::WaitCrc16LowByte:
            AcceptByte(val, true);
            innerState = InnerState::WaitCrc16HighByte;
            return Status::CrcLowByte;

        case InnerState::WaitCrc16HighByte:
            AcceptByte(val, true);
            if (!VerifyCRC()) {
                DeadState();
                return Status::BadCrc;
            }
            innerState = InnerState::WaitDataRetrive;
            return Status::FrameEnd;

        default:
            return Status::DecodeFailed;
        }
    }

    Status DeadState() {
        innerState = InnerState::StopOnDeath;
        return Status::DecodeFailed;
    }

    void AcceptByte(uint8_t val, bool isFrameData = false, bool isTagValue = false) {
        frameBuffer[frameLen] = val;
        frameLen++;
        if (isFrameData && frameDataLen > 0) {
            frameDataLen--;
        }
        if (isTagValue && curTlvLen > 0) {
            curTlvLen--;
        }
    }

    bool VerifyCRC() const {
        if (skipCrcVerify) {
            return true;
        }
        if (frameLen < 7) {
            return false;
        }
        uint16_t crc = frameBuffer[frameLen - 1];
        crc <<= 8;
        crc += frameBuffer[frameLen - 2];
        return crc16(frameBuffer, frameLen - 2) == crc;
    }

private:
    const bool skipCrcVerify;
    const uint8_t targetAddr;
    uint8_t* frameBuffer;
    size_t frameLen;
    uint8_t frameDataLen = 0, curTlvLen = 0;
    InnerState innerState = InnerState::WaitHeader;
};
}